A brake flush is often necessary to ensure that a car's brake system performs properly. It also helps the longevity of the brake system components. Brake fluid becomes contaminated with air, moisture and sludge over time, and a brake flush provides new, clean brake fluid.
The manufacturer's maintenance schedule makes suggestions as to when a car should undergo a brake flush. Typically, a brake flush is recommended every 36 months or 24,000 miles. If the brake pedal feels spongy when depressed or the brakes stop performing as expected, it could be a sign that the car needs a brake flush.